JPH1058214A - Air chuck for machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the initial grasping force of pawls for a work to be processed even if the revolving speed of a chuck body has increased. SOLUTION: Work grasping pawls for a work to be processed are attached in a chuck body 2 which is mounted on a rotary shaft such as spindle of a machine tool etc., and the chuck body 2 is furnished internally with air chambers to which air pressure for driving the pawls is supplied. A control system 56 includes an encoder to sense the revolving speed of a rotary shaft such as the spindle etc. of a machine tool, etc., and the air pressure to the air chambers is changed in compliance with the change in the revolving speed of the rotary shaft so as to cancel the change of the work grasping force resulting from the centrifugal force of the pawls. This allows maintaining the initial grasping force of the pawls for the work.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an air chuck used for a machine tool such as an NC lathe.

[0002]

2. Description of the Related Art An air chuck of this kind is disclosed in
As shown in Japanese Patent No. 7512, an air chamber for driving a piston by air pressure is provided in the chuck main body, and the piston in the air pressure is connected to the diaphragm.
A claw for gripping the work is attached to the diaphragm. When the piston is driven by air pressure, the diaphragm is deformed by the driving force of the piston, and the pawl is opened or closed to grip or release the work. The high-pressure air is supplied to or discharged from the air chamber of the chuck body through a three-layer tube connected to an air pump.

[0003]

An air chuck using a diaphragm has a very high accuracy of grasping a work, can grasp a work softly, and can set a grasping force suitable for processing the work. Also, since it is maintenance-free, it is most suitable for automation, grinding, etc. However, as the spindle speed of the machine tool increases, the gripping force decreases due to an increase in centrifugal force, and in some cases, there is a problem that the workpiece falls off during machining. In order to prevent this, setting is made higher than the appropriate gripping force in anticipation of a decrease in the gripping force due to centrifugal force.However, if the gripping force is increased, the workpiece will be deformed, distorted, etc. There is a problem that the accuracy of time cannot be maintained. Further, there is a problem that it is not suitable for high-speed rotation processing of a thin work. An object of the present invention is to solve the above problems.

[0004]

In order to achieve the above object, the present invention is mounted on a rotating shaft such as a main shaft of a machine tool,
A claw for gripping a work is attached, and a chuck body having an air chamber in which air pressure for driving the claw is supplied is provided, and air is supplied to and discharged from the air chamber by an air pressure feeding device. In a machine tool air chuck configured to drive the encoder, an encoder that converts the rotation speed of the rotation shaft into an electric signal, and an air control unit that controls air pressure to the air chamber according to the rotation speed of the rotation shaft. Provided, sensing the number of rotations of the rotating shaft, changing the air pressure to the air chamber according to the change in the number of rotations of the rotating shaft, canceling the change in the work gripping force due to the centrifugal force of the claw, This is to maintain the initial gripping force of the nail on the work. Further, in the present invention, a plurality of the air chambers are provided inside the chuck main body, a piston is arranged for each air chamber, each piston is connected to a diaphragm, and a claw for grasping a work is fixed to the diaphragm. Then, high-pressure air for a workpiece initial grasping force is supplied to at least one of the plurality of air chambers, and a control air pressure corresponding to a change in the rotation speed of the rotating shaft is supplied to the other air chambers. It is intended to be supplied. Further, in the present invention, the chuck body or a member that rotates in conjunction therewith is provided with a rotation-side air port that communicates with an air chamber to which the high-pressure air for the initial gripping force of the work is supplied. An air supply / discharge port communicating with the air pressure feeding device is disposed on the rotation side so as to face the rotation side air port, an air pressure holding valve is provided on the rotation side air port, and the air supply / discharge port is connected to the rotation side air port. To supply and discharge air to and from the rotating air port, and disconnect the air supply and discharging port from the rotating air port to close the air pressure holding valve. It is.

[0005]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Reference numeral 2 denotes an air chuck main body detachably mounted on an end face of a spindle of an NC machine tool, for example, a lathe. The air chuck main body 2 includes a base 4 having cylinder walls 4a and 4b formed in a cylindrical portion, a tubular portion 6a and a plate-like portion 6b. A base cover 6 having a disk-shaped portion 6b fixed to one end of the cylindrical portion of the base 4; and a diaphragm 8 having an outer portion fixed to the other end of the cylindrical portion of the base 4. Have been. A plurality of work grasping claws 10 are fixed on a circular line to the thin plate portion 8a of the diaphragm 8. Reference numeral 12 denotes a partition plate whose outer peripheral portion is fixed to the outer diameter portion of the diaphragm 8 and whose inner diameter portion is slidably fitted to the outer peripheral surface of the inner diameter portion of the diaphragm 8. Reference numerals 14 and 16 denote pistons, and the pistons 14 and 16 and the inner diameter of the diaphragm 8 are connected by bolts.

A tubular body 18 is screwed into the tubular portion 6a of the base cover 6. Tubular portion 6 of base cover 6
One of the inner tubes 18a is fitted to the inner peripheral surface of the cylindrical body 18a, and one of the middle tubes 18b is fitted to the inner peripheral surface of the cylindrical body 18 to form the tubular portion 6a of the base cover 6.
One of the outer tubes 18c is fitted and connected to the large-diameter inner peripheral surface. The inner, middle and outer tubes 18
a, 18b and 18c are made of steel pipes, and constitute an air supply / discharge tube 18 having a three-layer structure as a whole. The first air flow passage 20 of the air supply / discharge tube 18 is connected to the third air flow passage formed in the base cover 6, the base 4 and the piston 16 through the third air flow passage 20 in the air chuck body 2.
The air chamber 22 communicates with the first air chamber 24.

The second air flow passage 26 of the air supply / discharge tube 18 is connected to a fourth air chamber 28 and a second air chamber 30 via air flow passages formed in the base cover 6 and the base 4. Is in communication with When high-pressure air (air) is supplied from the first air flow passage 20 of the tube 18, this air is transmitted to the third and first air chambers 22 and 24 on one surface side of the pistons 14 and 16, 14 and 16 move rightward in FIG. In conjunction with the rightward movement of the pistons 14 and 16 in FIG. 2, the thin plate portion 8a of the diaphragm 8 is deformed in a rightward bending direction, and the work grasping claw 10 is reduced in diameter to grasp the work. Nail 1
The work (not shown) arranged between 0 is grasped by the work grasping claw 10. At this time, the pistons 14 and 1
The pressure in the fourth and second air chambers 28 and 30 on the other surface side of 6 is reduced. High-pressure air is supplied to the fourth and second air chambers 28 and 30, and the third and first air chambers 22 and 24 are supplied.
When the pressure is reduced, the pistons 14 and 16 move to the left in FIG. Thereby, the thin portion 8a of the diaphragm 8 is formed.
However, the work grasping claw 10 is bent in the left direction in FIG.

Reference numerals 32 and 34 denote holding bodies, which are integrally connected to each other by screwing, and a tubular block 36 is fixedly arranged on one of the holding bodies 32. The holders 32, 34
It is fixed to the body of the NC machine tool, for example, a lathe, that is, the non-rotating side. Reference numeral 38 denotes a support tube, which is rotatably supported by the holder 32 via a ball bearing so as not to move in the axial direction. The other end of the air supply tube 18 is fitted and fixed to the support tube 38. Fluid passages 40 and 42 are formed in the tubular block 36, and connectors 44 and 46 are connected to openings of the passages 40 and 42. The fluid passage 40 communicates with the second air flow passage 26 of the air supply / discharge tube 18 through a ring-shaped groove 48 formed in the inner diameter of the tubular block 36, and the fluid passage 42 communicates with the tubular block 36. It communicates with the first air flow passage 20 of the air supply / discharge tube 18 via a ring-shaped groove 50 formed in the inner diameter portion and a hole provided in the support tube 38.

A tube is connected to the connectors 44 and 46, and an air control valve 52 is disposed on each of the tubes.
Are connected to the output of a fluid pumping device comprising an air pump. The control unit of the air control valve 52 is connected to a digital analog voltage generation unit 54 as shown in FIG. 1, and is configured to control the air pressure according to the control input voltage as shown in FIG. I have. The digital / analog voltage generator 54 is connected to a control system 56 of the NC machine tool. In FIG. 1, 58
Is an input unit, 60 is a memory, 62 is a main program,
Reference numeral 64 denotes a rotation display unit for displaying the number of rotations of the main shaft, and 66 denotes a pulse encoder for converting the rotation of the main shaft into an electronic pulse signal. The memory 60 has a shape of a workpiece grasping claw,
Appropriate voltage data corresponding to the number of revolutions of the main shaft is stored in the form of a table according to the size, weight, and the like. Next, the operation of the present embodiment will be described.

When the workpiece is placed between the gripping claws 10 in a state where the workpiece gripping claw 10 is expanded (opened), and the chuck drive switch of the input unit 58 is pressed in this state, a digital analog The voltage signal for the initial grasping force is supplied to the voltage generation unit 54 to the control unit of the air control valve 52 for the first air flow passage 20. As a result, the high-pressure air for the initial grasping force is supplied to the first air flow passage 20, and the work is grasped by the work grasping claw 10 with the initial grasping force. This initial gripping force is set to an appropriate gripping force that does not cause deformation, distortion, or the like of the work. Next, the spindle is rotated to start cutting. The control system 56 counts input pulses from the pulse encoder 66 and measures the number of revolutions of the main shaft. The control system 56 controls the analog voltage generator 54 so that the analog voltage generator 54 outputs an appropriate voltage corresponding to the rotation speed of the spindle. The output of the analog voltage generator 54 is the first air The air is supplied to the air control valve 52 corresponding to the flow passage 20.

As a result, the centrifugal force generated in the work gripping claw 10 corresponding to the rotation speed of the main shaft is canceled, and the work is maintained in a state where the work is gripped with an appropriate initial gripping force regardless of the change in the rotation speed of the main shaft. Is done. Next, another embodiment of the present invention will be described with reference to FIGS. The first air flow passage 20 of the air supply / discharge tube 18 is connected to the air flow passage formed in the base cover 68 and the pistons 70 and 72.
Is communicated with the first air chamber 76 via an air flow passage formed in the inner diameter portion of the double piston 74 having the same.
The second air flow passage 26 of the air supply / discharge tube 18 communicates with the second air chamber 80 via an air flow passage formed in the base cover 68 and the base 78.

Reference numeral 82 denotes a partition plate, 84 denotes a diaphragm, 86
Numerals denote work grasping claws, and their configuration is the same as the configuration of the air chuck body 2 shown in FIG. A flange 88 is fixed to the base cover 68. The flange 88 is configured to be fixed to a spindle such as an NC lathe by bolts. Two cylindrical concave portions are formed on the outer peripheral portion of the flange 88, and cylindrical bodies 90 and 92 are fitted and fixed to the concave portions via O-rings.

The cylindrical bodies 90 and 92 have a tapered small-diameter portion and a large-diameter portion, and the small-diameter portion forms a rotation-side air port 94. Each of the large diameter parts has an air pressure holding valve 9
6, 98 valve bodies are arranged, and the axial opening / closing operation section 100 of each valve 96, 98 is slidably fitted to the rotation side air port 94. An O-ring 102 for sealing is fitted to the shaft portion of the valve body. The air pressure holding valves 96, 9
Inside 8 is formed an air hole 104 for opening and closing a valve.

The air pressure holding members 96 and 98 are urged by a coil spring 106 in a direction protruding from the outer peripheral surface of the flange 88.
Numeral 2 is configured to press against the wall surfaces of the inner diameter portions of the cylinders 90 and 92 to cut off the communication between the rotation-side air port 94 and the lower part of the cylinders 90 and 92. The lower part of the cylinder 92 communicates with the third air chamber 108 of the chuck body through an air flow passage. The lower part of the cylindrical body 90 communicates with the fourth air chamber 110 through an air flow passage. Reference numeral 112 denotes a valve operating body, which is attached to a non-rotating side of a machine body (not shown) of the machine tool via a lifting drive mechanism so as to be able to move up and down.

The valve operating body 112 has nozzles 114 and 11 at positions opposed to the rotation path of the rotation side air port 94.
6 is formed, and at the tip of each of the nozzles 114 and 116,
The air supply / discharge ports 118 and 120 are opened, and the air supply / discharge ports 118 and 120 are connected to the air pressure feeding device via a flexible high-pressure hose (not shown). An air control valve 122 is provided on each of the high pressure hoses communicating with the air supply / discharge ports 118 and 120. The control section of each air control valve 122 is connected to the digital / analog voltage generation section 54 and is configured to be controlled by the control system 56. The system for supplying air to the air supply / discharge tube 18 is the same as the embodiment shown in FIG.

Next, the operation of the present embodiment will be described.
The spindle is stopped at a predetermined position by numerical control of the control system 56, and the nozzles 114,
The opening of the opening / closing operation section 100 of the corresponding air pressure holding valves 96, 98 is accurately opposed to the opening 116. In this state,
The work is inserted and arranged between the work gripping claws 86 in the opened state. Next, when the chuck drive switch of the input unit 58 is pressed, a voltage signal for the initial grasping force is supplied to the digital analog voltage generation unit 54 to the control unit of the air control valve 122 for the nozzle 116. On the other hand, the valve operating body 112
Moves radially toward the flange 88, and the tips of the nozzles 114 and 116 abut and air-tightly contact the upper ends of the opening and closing operation parts 100 of the corresponding air pressure holding valves 96 and 98, respectively. The holding valves 96 and 98 are pushed down against the elastic force of the coil spring 106.

The air pressure holding valves 96 and 98 are connected to the flange 88
, The shut-off state of the rotation-side air port 94 is released, and the third and fourth air chambers 108 and 110 are released.
Communicates with the air pumping device. By controlling the air control valve 122, high-pressure air for an initial grasping force is supplied to the third air chamber 108, and the work is gripped by the work grasping claw 86 with the initial grasping force. This initial gripping force is set to an appropriate gripping force that does not cause deformation, distortion, or the like of the work. When the initial high-pressure air is supplied to the third air chamber 108, the air in the fourth air chamber 110 is discharged. Next, the valve operating body 112 is driven in a direction away from the flange 88, and the air pressure holding valves 96 and 98 are closed. As a result, the third air chamber 108 is maintained at the set initial gripping force air pressure.

Next, the main shaft is rotated to start cutting. The control system 56 counts input pulses from the pulse encoder 66 and measures the number of revolutions of the main shaft. The control system 56 controls the analog voltage generator 54 so that the analog voltage generator 54 outputs an appropriate voltage corresponding to the rotation speed of the spindle. The output of the analog voltage generator 54 is the first air Flow passage 20
The air is supplied to the air control valve 52 corresponding to the second air flow passage 26. As a result, the centrifugal force generated in the work grasping claw 86 corresponding to the rotation speed of the main shaft is canceled, and the state where the work is gripped with the proper initial setting grasping force is maintained regardless of the change in the rotation speed of the main shaft. .

[0019]

As described above, according to the present invention, the initial gripping force of the claw on the work is maintained even if the rotation axis of the machine tool changes, so that the work is not deformed or distorted.
There is an effect that a thin work can be easily processed.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present invention.

FIG. 2 is a sectional view of an air chuck.

FIG. 3 is a characteristic diagram of an air control vibe.

FIG. 4 is a block diagram showing another embodiment of the present invention.

FIG. 5 is a cross-sectional view of an air chuck main body showing another embodiment of the present invention.

FIG. 6 is a partial sectional view of an air chuck main body showing another embodiment of the present invention.

FIG. 7 is a bottom view of the valve operating body.

[Explanation of symbols]

 2 Air chuck body 4 Base 4a Cylinder wall 4b Cylinder wall 6 Base cover 6a Tubular part 6b Board-shaped part 8 Diaphragm 8a Thin part 10 Work grasping claw 12 Partition plate 14 Piston 16 Piston 18a Inner tube 18b Middle tube 18c Outer tube 18 Air Supply / discharge tube 20 first air flow path 22 third air chamber 24 first air chamber 26 second air flow path 28 fourth air chamber 30 second air chamber 32 holding body 34 holding body 36 tubular block 38 Support pipe 40 Fluid passage 42 Fluid passage 44 Connector 46 Connector 48 Groove 50 Groove 52 Air control valve 54 Digital analog voltage generator 56 Control system 68 Base cover 70 Piston 72 Piston 74 Double piston 76 First Air chamber 78 Base 80 Second air chamber 82 Partition plate 84 Diaphragm 86 Work grasping claw 88 Flange 90 Cylindrical body 92 Cylindrical body 94 Rotating air port 96 Air pressure holding valve 98 Air pressure holding valve 100 Opening / closing operation section 102 O-ring 104 Air Hole 106 Spring 108 Third air chamber 110 Fourth air chamber 112 Valve operating body 114 Nozzle 116 Nozzle 118 Air supply / discharge port 120 Air supply / discharge port 122 Air control valve

Claims (3)

[Claims] Claims: 1. A tool mounted on a rotating shaft such as a main shaft of a machine tool,
A claw for gripping a work is attached, and a chuck body having an air chamber in which air pressure for driving the claw is supplied is provided, and air is supplied to and discharged from the air chamber by an air pressure feeding device. In a machine tool air chuck configured to drive the encoder, an encoder that converts the rotation speed of the rotation shaft into an electric signal, and an air control unit that controls air pressure to the air chamber according to the rotation speed of the rotation shaft. Provided, sensing the number of rotations of the rotating shaft, changing the air pressure to the air chamber according to the change in the number of rotations of the rotating shaft, canceling the change in the work gripping force due to the centrifugal force of the claw, An air chuck for a machine tool, wherein an initial gripping force of a claw on a workpiece is maintained. 2. A plurality of air chambers are provided inside the chuck body, pistons are arranged for each air chamber, each piston is connected to a diaphragm, and a claw for grasping a work is fixed to the diaphragm. Supplying high-pressure air for initial grasping force to at least one of the plurality of air chambers, and supplying air pressure for control according to a change in the rotation speed of the rotating shaft to the other air chambers. The air chuck for a machine tool according to claim 1, wherein the air chuck is used. 3. The chuck body or a member that rotates in conjunction with the chuck body is provided with a rotation-side air port that communicates with an air chamber to which the high-pressure air for the initial gripping force of the work is supplied. An air supply / discharge port communicating with the air pressure feeding device is disposed on the side facing the rotation side air port, an air pressure holding valve is provided on the rotation side air port, and the air supply / discharge port is connected to the rotation side air port. It is configured to supply and discharge air to and from the rotation side air port by being connected, and to disconnect the air supply and discharge port and the rotation side air port to close the air pressure holding valve. The air chuck for a machine tool according to claim 2, wherein: